I am dealing with [35,6] linear code over finite filed with 2 elements. I am able to get an output of its generator matrix as 6x35 matrix, but while computing parity check matrix which will be of size 29x35, I am getting following output: IndexError:string index out of range
Does it mean that its size is two large? If still it is so, how to get that matrix in sage??
ithout further information on your concrete use case, such an error appears when you asks for the letter of a string at an index that is larger than the length of the string:
sage: s = 'abc'
sage: s[0]
'a'
sage: s[1]
'b'
sage: s[2]
'c'
sage: s[3]
IndexError: string index out of range
The following was working for me. A is a matrix of shape 6x35, taken (almost) randomly. (There was a rank check after getting it.) C is the linear code associated to it. B is the parity check matrix for the code.
sage: A = MatrixSpace( GF(2), 6, 35 ).random_element()
sage: A
[1 1 1 1 0 1 1 0 0 1 1 0 1 0 0 0 1 1 1 1 1 0 0 1 1 1 0 1 1 0 1 1 1 0 1]
[1 0 0 0 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 0 1 1 0 0 0 1 1 1]
[1 0 0 0 0 0 1 1 1 1 1 1 1 1 0 1 1 1 0 0 1 0 0 1 1 1 0 1 0 1 0 1 1 0 1]
[0 1 1 0 1 1 1 1 1 1 0 0 0 0 0 1 0 1 1 0 1 1 1 1 1 0 0 0 1 1 0 1 0 1 1]
[0 1 0 1 0 1 0 0 0 0 1 1 0 1 1 1 0 1 0 0 1 0 0 0 0 0 1 1 0 0 1 0 0 1 1]
[1 0 0 0 1 0 1 0 0 1 0 0 0 1 0 0 1 0 1 0 1 1 1 1 1 1 1 0 1 0 1 0 0 1 0]
sage: A.rank()
6
sage: # this is ok...
sage: C = LinearCode(A)
sage: B = C.parity_check_matrix()
sage: B
29 x 35 dense matrix over Finite Field of size 2 (use the '.str()' method to see the entries)
Asked: 2016-12-04 13:45:49 +0100
Seen: 603 times
Last updated: Mar 29 '17
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Could you please provide the full code that lead to the error ?